The present invention relates to synchronization methods for a redundantly structured automation system consisting of at least two subsystems interconnected via communication means. The present invention also relates to a method for generating a sequence of machine instructions from an application program for the subsystems of a redundantly structured automation system consisting of at least two subsystems.
Synchronization methods for automation systems are generally known. The automation system can work, for example, in clock-controlled or in event-controlled synchronism. Furthermore, the European Patent Application No. EP 0 497 147 A2 discusses a method for operating a redundantly structured programmable controller consisting of two subunits, in which the subsystems synchronize themselves, at the latest, after an expiration of a time preselectable by the user.
In methods known heretofore, any jumps (branching) occurring in the programs executed by the subsystems cause the "previous history" (previous state) to be lost. As a consequence, the subsystem in question can no longer determine when the last synchronization was performed. This in turn, requires a synchronization before any jump (branching) instruction. In this respect, the method according to the European Patent Application No. EP 0 497 147 A2 is not optimal since extra time is spent unnecessarily on the synchronization.
Therefore, there exists a need to definitely and reliably guarantee a reproducible alarm-reaction time, given the lowest possible degree of complexity, for synchronization tasks. Moreover, there exists a need to allow the computing capacity of the automation system to be better utilized by minimizing the degree of complexity required for synchronization. Furthermore, avoiding manual interventions in the application program, which could cause errors, is also desired.